It is known in the art of broaching to carry a series of work forming tools on an endless chain which can be driven so as to bring the tools into successive engagement with one or more workpieces. In addition, prior patents have disclosed the use of this type of machinery for forming spur and helical gears, although the applicant herein is unaware of any commercially successful gear forming machine which utilizes a chain for carrying tools for the manufacture of such precision products as gears.
Separate patents have disclosed separate arrangements for designing and assembling machinery for manufacturing gears. It is known, for example, from U.S. Pat. No. 1,469,602 to provide for a spiral arrangement of cutting tools about the working face of an endless chain means so that gear teeth can be formed in a workpiece by rotating the workpiece as the chain is rotated in a timed, working engagement with the workpiece. In this type of process individual tools remove stock from the workpiece as the workpiece rotates, and this process is continued until all of the cutting tools have passed through all of the tooth slots of the workpiece to develop a complete tooth profile. This type of process will be referred to herein as a hobbing process. Separately, it is known from U.S. Pat. Nos. 1,468,393; 2,475,690; and 2,749,804, for example, to provide for multiple rows of gear cutting tools arranged in parallel paths across the face of an endless chain for contacting a workpiece as the workpiece is rolled (or translated) relative to the working face of the chain. This type of operation will be referred to herein as a roll generating process.
There are different job applications where it may be desirable to use either the hobbing method or roll generating method (or variations thereof) for meeting specific production or quality requirements for the job. For example, the hobbing type of process offers higher production rates and is suitable for long production runs of the type that might be expected for fine pitch helical gears used in automotive applications. The generating process is slower but offers lower cost of tooling and versatility for jobbing type work or for manufacture of coarse pitch spur gears. These needs could be satisfied by utilizing separate machines for separate jobs, but obviously, such an approach involves a major investment in different types of machinery capable of carrying out the different manufacturing processes described above. In contrast, the present invention provides for a very versatile single machine which can be adjusted and set up to accommodate different processing requirements. A major feature of the machine of the present invention is its special drive train system which includes easily connected and disconnected components for effectively altering the operation of the machine from one type of cutting process to another.
According to a preferred embodiment of the invention, a gear manufacturing apparatus of the type having a series of stock removing tools carried on a drive endless chain is provided with a first drive train for driving the endless chain and a first (or main) drive motor operatively connected to the first drive train for imparting controlled driving motion to the endless chain. In addition, there is a second drive train for imparting a controlled rotating motion to the workpiece while the workpiece is presented to the stock removing tools carried by the endless chain. The second drive train can be selectively connected or disconnected to the first drive train to provide for two separate modes of operation for the machne.
In a first mode, the second drive train is connected to the first drive train, and this results in a timed relationship between the speed of movement of the stock removing tools relative to the speed of rotation of the workpiece. This mode is used for hobbing operations of the machine.
In a second mode, the second drive train is disconnected from the first drive train and is connected to a second drive motor for independently controlling the workpiece relative to movement of the stock removing tools. In this mode, an indexing system is operatively associated with the second drive train for providing periodic rotations of the workpiece while it is being formed into a gear. In this respect the second drive train is substantially identical to a generating drive train used in certain bevel gear cutting machines manufactured by The Gleason Works (see U.S. Pat. No. 3,971,293). Traversing means are also provided for translating the workpiece and the cutting tools relative to each other when the machine is set up to operate in this second mode. This second mode is used for generating operations of the machine. An improved generating method involves the use of a single row of tools on the endless chain for forming one, precisely controlled, tooth slot at a time in an indexing workpiece. This method is similar to known methods for forming single tooth slots in bevel gears,but has not, as far as is known, been used with an endless chain apparatus for forming spur and helical gears.
These and other features and advantages of the invention will become apparent in a more detailed discussion which follows. In that discussion reference will be made to the accompanying drawings as briefly described below.